Red and orange laser operation of Pr:KYF4 pumped by a Nd:YAG/LBO laser at 469.1nm and a InGaN laser diode at 444nm

We report the basic luminescence properties and the continuous-wave (CW) laser operation of a Pr3+-doped KYF4 single crystal in the Red and Orange spectral regions by using a new pumping scheme. The pump source is an especially developed, compact, slightly tunable and intra-cavity frequency-doubled diode-pumped Nd:YAG laser delivering a CW output power up to about 1.4 W around 469.1 nm. At this pump wavelength, red and orange laser emissions are obtained at about 642.3 and 605.5 nm, with maximum output powers of 11.3 and 1 mW and associated slope efficiencies of 9.3% and 3.4%, with respect to absorbed pump powers, respectively. For comparison, the Pr:KYF4 crystal is also pumped by a InGaN blue laser diode operating around 444 nm. In this case, the same red and orange lasers are obtained, but with maximum output powers of 7.8 and 2 mW and the associated slope efficiencies of 7 and 5.8%, respectively. Wavelength tuning for the two lasers is demonstrated by slightly tilting the crystal. Orange laser operation and laser wavelength tuning are reported for the first time

De la représentativité à la spécialisation : exemple d’un petit corpus sur la synonymie

La notion de petit corpus nécessite une réflexion épistémologique pour se situer dans le paysage des sciences du langage. La taille du corpus ne pouvant suffire pour départager les petits corpus des grands corpus, la ligne de partage se situe au niveau de la représentativité et des objectifs de recherche. Le petit corpus est constitué en vue d’un objectif de recherche mené sur un domaine précis de la langue et du discours pour tenir compte des influences du type de discours et du genre sur les phénomènes linguistiques étudiés. Le petit corpus doit donc rendre compte de ce champ d’investigation particulier. La spécialisation du corpus lui confère donc sa représentativité. Pour aboutir à cette spécialisation, il est nécessaire d’établir un corpus homogène concernant les paramètres textuels, (discours, type de texte, genre, etc.). Par ailleurs, le petit corpus rend possible un retour au contexte linguistique et situationnel : une connaissance approfondie des textes favorise l’interprétation des données. Afin d’illustrer ces propos sur les petits corpus, un corpus construit dans le cadre d’une recherche menée sur la synonymie selon une approche onomasiologique et syntagmatique est présenté. Au-delà de sa petite taille, ce corpus tire sa spécialisation de son homogénéité : les paramètres textuels ont été neutralisés, puisque les textes du corpus appartiennent tous au même discours, au même type de texte et au même genre. La recherche onomasiologique suppose d’ajouter un paramètre thématique lors de la constitution du corpus : les textes choisis doivent manifester de façon saillante la même thématique. Si les paramètres textuels semblent les plus évidents pour spécialiser un corpus, d’autres paramètres inhérents à l’objectif de recherche interviennent.Small corpora need epistemological reflection to be set into the field of language sciences. The size of the corpus can not be enough to make a distinction between small corpora and big corpora, because the real distinction is about representativity and research objectives. A small corpus is built according to a research objective about a specific area of language to take into account the effects of type of discourse and genre on linguistic phenomena. The small corpus must be a representation of this specific field of research. As it is specialised, a small corpus can be representative. But to be specialised, a corpus must be homogeneous about textual parameters such as discourse, type of text or genre. Besides, with a small corpus, it is possible to be aware of the linguistic and situational context of texts : a detailed knowledge of the texts facilitate the interpretation of data. To illustrate these reflections about small corpora, a corpus built for a research about synonymy according to an onomasiological and syntagmatic approach is presented. Besides its small size, this corpus is specialised because of its homogeneity : the textual parameters have been neutralised, given that the texts of the corpus belong to the same discourse, the same type of text and the same genre. The onomasiological approach needs another parameters to build the corpus : a topic that must be relevant in all the texts of the corpus. If the textual parameters seem obvious and necessary to build a specialised corpus, other parameters, such as topic, depend on specific research objectives

Rare-Earth-Doped Low Phonon Energy Halide Crystals for Mid-Infrared Laser Sources

International audienceSince ~15 years, solid state lasers emitting in bands II (2.7-4.3, 4.5-5.2 µm) and III (8-14 m) of the atmosphere transparency spectral range are being developed for imaging, polluting species detection as well as military NRBC detection and optronic countermeasures. Because most of these applications require highly brilliant and/or important peak power laser sources, several RE$^{3+}$-doped (RE=rare earth) low phonon energy (ħ$\omega$<400 cm$^{-1}$) chloride and bromide crystals, such as APb$_2$X$_5$ (A=K,Rb;X=Cl,Br) or CsCdBr$_3$, stand out as promising laser gain media in the mid-infrared (MIR) spectral range [Doualan & Moncorgé, 2003; Isaenko et al., 2008

Visible laser operation of Pr3+-doped fluoride crystals pumped by a 469 nm blue laser

French National Research Agency (ANR)We report continuous-wave (CW) laser operation of Pr3+-doped LiLuY4, LiYF4 and KY3F10 single crystals in the Red, Orange and Green spectral regions by using a new pumping scheme. The pump source is an especially developed compact, slightly tunable and intracavity frequency-doubled diode-pumped Nd:YAG laser delivering a CW output power of 0.9W at 469.12 nm. At this pump wavelength, efficient room temperature laser emissions corresponding to the P-3(0)-> F-3(2), P-3(0)-> H-3(6) and P-3(1)-> H-3(5) Pr3+ transitions are observed. While a maximum slope efficiency of 45% is obtained in the red with Pr:LiYF4, the demonstration is made for the first time of the orange laser operation of Pr:KY3F10 at about 610 nm. (C) 2011 Optical Society of Americ

Diode-pumped regenerative Yb:SrF2 amplifier

International audienceWe report what we believe to be the first Yb:SrF2 regenerative femtosecond amplifier. The regenerative amplifier produces 325-fs pulses at 100-Hz repetition rate with an energy before compression of 1.4 mJ. The interest of Yb:SrF2 in such regenerative amplifiers and its complementarity to its well-known isotype Yb:CaF2 is also discussed

Diode-pumped Yb:CaF 2 multipass amplifier producing 50 mJ with dynamic analysis for high repetition rate operation

International audienceThe dynamic thermal issues of the Yb:CaF 2 crystals within a multi-tens-mJ-energy multipass amplifier operating in the 20–100 Hz repetition rate range and pumped in quasi-cw regime have been studied at different timescales. Thermal response times of the system have been precisely investigated and analyzed, for the first time to our best knowledge in such amplifiers. This study includes a dual timescale analysis: in the long-timescale (second) with direct thermography mapping and in the millisecond range with thermal lensing in a pump-probe configuration. Very atypical positive lens behavior with fluorites will also be presented and discussed. This complete analysis is used to demonstrate the capability of Yb:CaF 2 multipass amplifier systems for operating the amplifier at 20 Hz with 57 mJ and 100 Hz with 32-mJ stable regime. Indeed, high repetition rate multipass amplifier has been realized for the first time with Yb:CaF 2 and for this energy. The results have been analyzed precisely to take into account the thermal issues and excellent beam quality, with a M 2 of 1.1. The pointing stability of 20 lrad has been measured documenting the reliability of the high repetition rate mJ amplifier

On Yb:CaF2 and Yb:SrF2 : Review of spectroscopic and thermal properties and their impact on femtosecond and high power laser performance

International audienceWe present an overview of laser results we obtained with Yb-doped calcium fluoride and its isotype strontium fluoride. In order to study the laser performance in femtosecond and high power regimes, spectral and thermal properties are first discussed including the potential of these crystals at room and cryogenic temperatures. Experimental demonstrations of high-power and ultrashort pulse oscillators and amplifiers are presented and analyzed

Mode-locked operation of a diode-pumped femtosecond Yb : SrF2 laser

International audienceFemtosecond mode-locked operation is demonstrated for the first time, to our knowledge, with a Yb:SrF2 crystal. The shortest pulse duration is 143 fs for an average power of 450 mW. The highest average power is 620 mW for a pulse duration of 173 fs. Since Yb:SrF2 corresponds to the longest-lifetime Yb-doped crystal with which the mode-locking operation has been achieved, a detailed analysis is carried out to characterize the quality of the solitonlike regime

High-power diode-pumped cryogenically cooled Yb:CaF2 laser with extremely low quantum defect

International audienceHigh-power diode-pumped laser operation at 992-993nm under a pumping wavelength of 981 of 986nm is demonstrated with Yb:CaF2 operating at cryogenic temperature (77K), leading to extremely low quantum defects of 1.2% and 0.7%, respectively. An average output power of 33Whas been produced with an optical efficiency of 35%. This represents, to the best of our knowledge, the best laser performance ever obtained at such low quantum defects on intense laser lines

Co-doped Dy3+ and Pr3+ Ga5Ge20Sb10S65 fibers for mid-infrared broad emission

Rare earth ion doped materials are means to obtain cost-effective infrared light sources, with enough brilliance for applications such as gas sensing. Within a sulfide matrix, the simultaneous luminescence of both Pr3+ and Dy3+ in the Ga5Ge20Sb10S65 glass is reported. The use of these two rare earths is giving rise to a broad continuous luminescence in the 2.2–5.5 µm wavelength range, which could be used as a mid-infrared light source for gas-sensing applications. The demonstration of CO2 and CH4 detection using a fiber drawn from these materials is reported